Genetic Attributes/Genetic Diversity
The nested relationship
of genetic diversity within populations and the diversity of populations within
species is illustrated in the lower part of the "Levels of Biodiversity"
diagram.
At the bottom, labeled as "gene types," there are several sets of small
shaded circles, each set symbolizing the range of genetic variants or types ("alleles")
of a single gene potentially found in a population.
Above these circles are horizontal bars, representing the actual amount of genetic
variation found in several different hypothetical populations. The boxes drawn
around the sets of populationbars represent species.
Some species are made up of many populations (in this simple example, six is the
maximum), while others have fewer (e.g., species C with only four populations).
The amount of genetic variation contained in populations and species may also
vary; some species contain populations with a large amount of genetic variation
(such as A1), while others have populations with little genetic variation (e.g.,
B2).
In species D, substantial genetic variation (g-j) has been lost from all surviving
populations. In contrast, Species C illustrates how several populations, each
with relatively little genetic diversity, can preserve total genetic diversity.
If any of these four populations go extinct, however, some genetic richness will
be irretrievably lost.
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